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Abstract:

The practical transmission range of an electrical cable can be extended
by converting between electrical and optical signals using an
HDMI-optical converter that receives an SFP+ optics transceiver. A pair
of SFP+-based HDMI adapters/extenders can connect to a pair of HDMI
cables, where one of the HDMI cables is connected to an HDMI Source and
one of the HDMI cables is connected to an HDMI Sink. Each of the
SFP+-based HDMI cable extenders can terminate with an SFP+ port to house
a hot pluggable SFP+ transceiver. The apparatus can transmit 10 G video
data to the distance that is supported by the SFP+ product.

Claims:

1. An HDMI (High-Definition Multimedia Interface)-SFP+ (Enhanced small
form-factor pluggable) converter, comprising: a first converter that
converts HDMI signals of a first type to SFI signals of a second type;
and a second converter that converts the SFI signals of the second type
to the HDMI signals of the first type, wherein the signals of the first
type comprise HDMI electrical signals and the signals of the second type
comprise SFI electrical signals, and wherein the second converter
recovers an HDMI clock signal present in the HDMI signals of the first
type that are input to the first converter.

2. The converter of claim 1, wherein the first converter further
comprises: an HDMI to XGMII converter that receives HDMI signals and
converts the HDMI signals to XGMII signals; an XGMII to XAUI converter
that receives the XGMII and converts the XGMII signals to XAUI signals;
and an XAUI to SFI converter that receives the XAUI signals and converts
the XAUI signals to SFI signals, the XAUI to SFI converter transmitting
the SFI signals to an SFP+ optical transceiver.

3. The converter of claim 2, wherein the first converter converts 10-bit
data of the HDMI signals to 8-bit XGMII data.

4. The converter of claim 3, wherein 2 bits of the HDMI signals are
removed from the 10-bit data, and wherein the 2 bits are associated with
redundancy and error checking.

5. The converter of claim 3, wherein conversion of the 10-bit data of the
HDMI signals to 8-bit XGMII data is performed in accordance with a data
rate of the HDMI signals.

6. The converter of claim 5, wherein the conversion is performed when a
Transition Minimized Differential Signaling (TMDS) clock speed is greater
than 320 MHz.

7. The converter of claim 1, wherein the second converter further
comprises: an SFI to XAUI converter that receives SFI signals and
converts the SFI signals to XAUI signals; an XAUI to XGMII converter that
receives the XAUI signals from the SFI to XAUI converter and converts the
XAUI signals to XGMII signals; and an XGMII to HDMI converter that
receives the XGMII signals from the XAUI to XGMII converter and converts
the XGMII signals to HDMI signals.

8. The converter of claim 7, wherein the HDMI clock signal is recovered
from the XGMII signals by the second converter.

9. The converter of claim 1, wherein an HDMI source provides the HDMI
signals, and wherein the HDMI source comprises one of a set-top box, a
DVD player, a Blu-ray player, a digital video recorder, or a personal
computer.

10. The converter of claim 1, wherein an HDMI sink receives the HDMI
signals from the second converter, and wherein the HDMI sink comprises a
display device.

11. A method of transmitting an HDMI signal from an HDMI source to an
HDMI sink, comprising: converting the HDMI signal received from the HDMI
source to an optical signal; transmitting the optical signal over an
optical cable; receiving the optical signal from the optical cable;
converting the optical signal back to the HDMI signal; and outputting the
HDMI signal to the HDMI sink.

12. The method of claim 11, wherein converting the HDMI signal to optical
signal comprises: converting an HDMI signal to a XGMII signal; converting
the XGMII signal to a XAUI signal; converting the XAUI signal to an SFI
signal; and converting the SFI signal to an optical signal.

13. The method of claim 12, further comprising converting 10-bit data of
the HDMI signal to 8-bit XGMII data.

14. The method of claim 13, wherein the converting is performed in
accordance with a data rate of the HDMI signal.

15. The method of claim 14, wherein the conversion is performed when a
Transmission Minimized Differential Signaling (TMDS) clock speed is
greater than 320 MHz.

16. The method of claim 11, wherein converting the optical signal back to
the HDMI signal comprises: converting an optical signal to an SFI signal;
converting the SFI signal to a XAUI signal; converting the XAUI signal to
an XGMII signal; and converting the XGMII signal to the HDMI signal.

17. The method of claim 16, further comprising recovering an HDMI clock
signal from the XGMII signal.

18. An HDMI transmission path extension apparatus, comprising: an HDMI
(High-Definition Multimedia Interface) to SFP+ (small form-factor
pluggable) converter; an optical communications link; and an SFP+ to HDMI
converter, wherein the HDMI to SFP+ converter converts 10-bit data of
received HDMI signals to 8-bit data in accordance with a Transmission
Minimized Differential Signaling (TMDS) clock speed, and wherein the SFP+
to HDMI converter recovers an HDMI clock signal present in the HDMI
signals input to the HDMI to SFP+ converter.

19. The apparatus of claim 18, wherein the HDMI to SFP+ further
comprises: an HDMI to XGMII converter that receives HDMI signals and
converts the HDMI signals to XGMII signals; an XGMII to XAUI converter
that receives the XGMII and converts the XGMII signals to XAUI signals;
and an XAUI to SFI converter that receives the XAUI signals and converts
the XAUI signals to SFI signals, the XAUI to SFI converter transmitting
the SFI signals to an SFP+ optical transceiver.

20. The apparatus of claim 18, wherein the SFP+ to HDMI converter further
comprises: an SFI to XAUI converter that receives SFI signals and
converts the SFI signals to XAUI signals; an XAUI to XGMII converter that
receives the XAUI signals from the SFI to XAUI converter and converts the
XAUI signals to XGMII signals; and an XGMII to HDMI converter that
receives the XGMII signals from the XAUI to XGMII converter and converts
the XGMII signals to HDMI signals.

Description:

BACKGROUND

[0001] The transmission of digital video is a driving force in the growth
of networking and the Internet. Video is also driving the expansion of
wavelength-division multiplexing (WDM) transport networks that transmit
data at a maximum rate of 10.3125 Gigabits per second (Gbps) per
wavelength. A popular digital video interconnect interface is HDMI
(High-Definition Multimedia Interface), which is a digital alternative to
consumer analog standards such as radio frequency, coaxial cable and so
on. HDMI is a compact audio/video interface for transmitting uncompressed
digital data. HDMI cables can connect digital audio/video sources
including but not limited to set-top boxes, DVD players, Blu-ray players,
personal computers, etc. to compatible digital audio/video devices,
computer monitors, and digital televisions, etc. HDMI version 1.3 and 1.4
can transmit digital data at rates up to 10.2 Gbps but a typical HDMI
cable length is less than ten meters. Although no maximum length for an
HDMI cable is specified, signal attenuation limits useable lengths in
practice. In practice HDMI cables rarely exceed twenty-five feet.

[0002] The SFP (small form-factor pluggable) module is a compact
transceiver used for telecommunication and data communications
applications. It typically interfaces a network device motherboard for a
switch, router or media converter to a fiber optic or copper networking
cable. SFP transceivers support a number of communications standards
including SONET, Ethernet Fibre Channel and others. SFP+ is an enhanced
small form-factor pluggable module that supports data rates up to 10
Gbps. Its low cost makes widespread adoption of the 10 GE (10 Gigabit
Ethernet) standard more attractive.

SUMMARY

[0003] The reach of an HDMI cable can be extended by an apparatus that
converts electrical signals to optical signals and converts optical
signals to electrical signals. A pair of SFP+-based HDMI
adapters/extenders can connect to a pair of HDMI cables, where one of the
HDMI cables is connected to an HDMI Source and one of the HDMI cables is
connected to an HDMI Sink. Each of the SFP+-based HDMI cable extenders
can terminate with an SFP+ port to house a hot pluggable SFP+
transceiver. The apparatus can support the distance that is supported by
the SFP+ product.

[0004] In accordance with some implementations, there is provided an HDMI
(High-Definition Multimedia Interface)-SFP+ (Enhanced small form-factor
pluggable) converter that includes a first converter that converts HDMI
signals of a first type to SFP signals of a second type, and a second
converter that converts the SFP signals of the second type to the HDMI
signals of the first type. The signals of the first type may comprise
electrical signals and the signals of the second type may comprise
optical signals. The second converter may recover an HDMI clock signal
present in the HDMI signals of the first type that are input to the first
converter.

[0005] In accordance with some implementations, there is provided a method
of transmitting an HDMI signal from an HDMI source to an HDMI sink. The
method may include converting the HDMI signal received from the HDMI
source to an optical signal; transmitting the optical signal over an
optical cable; receiving the optical signal from the optical cable;
converting the optical signal back to the HDMI signal; and outputting the
HDMI signal to the HDMI sink.

[0006] In accordance with some implementations, there is provided an HDMI
transmission path extension apparatus. The extension apparatus may
include an HDMI to SFP+ converter, an optical communications link, and an
SFP+ to HDMI converter. The HDMI to SFP+ converter may convert 10-bit
data of received HDMI signals to 8-bit data in accordance with a
Transmission Minimized Differential Signaling (TMDS) clock speed. The
SFP+ to HDMI converter may recover an HDMI clock signal present in the
HDMI signals input to the HDMI to SFP+ converter.

[0007] This summary is provided to introduce a selection of concepts in a
simplified form that are further described below in the detailed
description. This summary is not intended to identify key features or
essential features of the claimed subject matter, nor is it intended to
be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a block diagram of an example of an end-to-end connection
using an HDMI-SFP+ adapter/extender in accordance with aspects of the
subject matter disclosed herein;

[0009]FIG. 2 is a more detailed block diagram of an example of FIG. 1 in
accordance with aspects of the subject matter disclosed herein; and

[0010]FIG. 3 is a flow diagram of an example of a process to extend the
reach of an HDMI cable using an HDMI-SFP+ adapter/extender in accordance
with aspects of the subject matter described herein.

DETAILED DESCRIPTION

Overview

[0011] As noted above, there is a practical limit as to the distance
between an HDMI source (e.g., a Blu-ray player, DVR, cable set-top box,
or other source of content) and a HDMI sink (e.g., a television or
monitor or other display device) can be connected with a cable. That
limit is e.g., about 10 meters, where a longer cable will like fail to
maintain the quality of video resolution that HDMI Revision 1.3/1.4 10.2
Gbps Transmission Minimized Differential Signaling (TMDS) can support. In
particular, a passive or standard HDMI cable can support data rates up to
10.2 Gbps but only for short distances. The reach of an HDMI cable with a
built-in booster or amplifier can extend to about 15 meters but can
transfer data at a maximum of only about 6.75 Gbps over TMDS. Existing
HDMI extenders can extend the useful reach of an HDMI cable to about 33
to 300 meters but cannot support a full data rate of 10.2 Gbps.

[0012] The subject matter described herein addresses HDMI cable distance
limitations arising in high-definition (HD) televisions, set-top boxes,
DVD recorders, Home Cinema and other devices by extending the reach of an
HDMI cable by using an HDMI-SFP+ adapter/extender such that the distance
between the source and sink can be extended indefinitely, dependent on
the optical characteristics of the SFP+ module used. SFP+ modules convert
between optical and electrical signals. An SFP+ module does no clock and
data recovery. SFP+ modules share a common physical form factor with
legacy SFP modules.

[0013] As will be described herein, HDMI cable reach can be extended using
the SFP+ adapter/extender and 10 GE SFP+ transceivers of the present
disclosure. Useful cable reach can be extended to 300 meters using a pair
of multi-mode optical fiber cables such as, for example, OM3, as defined
by the IEEE 802.3 ae standard. The reach can be further extended using
single-mode fibers for 10 GE SFP+ optics and an IEC 61754-20 compliant
optic fiber connector such as a Lucent connector (LC). Maximum available
resolution for 10.2 Gbps can be supported using a 10 gigabit Ethernet (10
GE) integrated circuit. Video quality, including resolution, refresh rate
and color depth can thereby be improved. The maximum resolution over a
single link at 24-bit/pixels (px) can be 2560×1600p75 at 9.986 Gbps
bandwidth. The maximum resolution over a single link at 30-bit/px can be
2560×1600 at 60 Hertz (Hz) at a bandwidth of 9.986 Gbps. The
maximum resolution over a single link at 36-bit/px can be 1920×1200
at 75 Hz at a bandwidth of 8.647 Gbps and 4096×2160 at 24 Hz at a
bandwidth of 10.083 Gbps. The maximum resolution over a single link at
48-bit/px can be 1920×1200p75 at a bandwidth of 9.224 Gbps and
1920×1200p60 at a bandwidth of 9.224 Gbps. 30-bit/px, 36-bit/px and
48-bit/px are sometimes referred to as "deep color mode".

[0014]FIG. 1 illustrates an example of an end-to-end connection 100 using
an HDMI-SFP+ adapter/extender in accordance with aspects of the subject
matter disclosed herein. HDMI is an audio/video interface for
transmitting uncompressed digital data. An HDMI source device such as
HDMI source 108 can be a digital audio/video (AV) source such as but not
limited to a set-top box, upconvert DVD player, HD DVD player, Blu-ray
Disc player, Advanced Video Coding High Definition (AVCHD) camcorder,
personal computer (PC), video game console (e.g., PlayStation 3, Xbox
360, AV receiver and other similar devices) and so on.

[0015] One end of an HDMI cable such as HDMI cable 112 can be connected to
the HDMI source 108 by insertion of the cable end into a port such as an
HDMI 19-pin connector in the HDMI source, the port constructed to receive
an HDMI cable end. The other end of the HDMI cable can be connected to a
transmit side SFP+ adapter/extender such as transmit side SFP+ adapter
102, as described herein. The transmit side SFP+ adapter/extender can be
constructed to have a port to receive the HDMI cable end. The transmit
side SFP+ adapter can also include a port such as port 116 that can
receive an SFP+ transceiver module such as SFP+ optics transceiver 104.
The SFP+ module can interface a network device motherboard or logic board
for the transmit side SFP+ adapter/extender to a fiber optic or copper
networking cable such as cable 120. The SFP+ module (e.g. SFP+ optics
transceiver 104) can support data rates up to 10 GE (10.3126 Gbps). Cable
120 can connect to a second SFP+ optics transceiver 104 plugged into a
second SFP+ adapter/extender such as receive side SFP+ adapter/extender
106. The receive side SFP+ adapter/extender 106 can be connected to a
second HDMI cable 114 connected to an HDMI sink such as HDMI sink 110.
HDMI sink 110 can be any suitable display device including but not
limited to a digital television, computer monitor or similar device.

[0016]FIG. 2 illustrates a more detailed example of portions of FIG. 1 in
accordance with aspects of the subject matter disclosed herein. An HDMI
source such as HDMI source 108 as described above typically includes an
HDMI transmitter such as HDMI transmitter 202 for transmitting data. The
HDMI transmitter can employ Transition Minimized Differential Signaling
(TMDS), a technology for transmitting high-speed serial data often used
by HDMI and Digital Visual Interface (DVI) as well as other digital
communication interfaces.

[0017] An HDMI transmitter typically receives video, audio and control
status information from HDMI source 108. Three TMDS differential pairs
are typically used to transfer the video data, each of the three
differential pairs or links corresponding to a different red-green-blue
(RGB) component. In FIG. 2, three data/control data channels are
represented in FIG. 2 by TMDS data channel 0 204a, TMDS data channel 1
204b and TMDS control channel 2 204c. The fourth TMDS channel, TMDS clock
channel 204d represents a clock signal generated by the HDMI transmitter,
used to coordinate signal processing.

[0018] TMDS uses a form of encoding on Video Data. The first stage of the
two-stage process converts an input of 8 bits into a 10 bit code with
particular properties. In the first stage, the first bit is untransformed
and each subsequent bit is either XOR or XNOR transformed against the
previous bit. The encoder chooses between XOR and XNOR by determining
which will result in the fewest transitions. The ninth bit encodes which
operation was used. In the second stage, the first eight bits are
optionally inverted to even out the balance of ones and zeros and
therefore the sustained average direct current level. The tenth bit
encodes whether or not this inversion took place.

[0019] The 10-bit TMDS symbol can represent either an 8-bit data value
during normal data transmission, or 2 bits of control signals during
screen blanking. Of the 1,024 possible combinations of the 10 transmitted
bits, 460 combinations are used for representing an 8-bit data value, 4
combinations are used for representing 2 bits of control signals (such as
horizontal synchronization (Hsync) and vertical synchronization (VSync)).
The remaining 560 combinations are reserved. Control data characters are
designed to have a large number of transitions (e.g., 7) to help the
receiver synchronize its clock with the transmitter clock.

[0020] In FIG. 2, a transmit side HDMI-SFP+ adapter/extender 102 can
include one or more of the following: an HDMI to XGMII converter 206, an
XGMII to XAUI converter 212 and an XAUI to SFI converter 216. The digital
information sent on the four TMDS channels by the HDMI transmitter 202
can be received by an HDMI to XGMII converter 206. XGMII (10 Gigabit
Media Independent Interface) is a standard defined in IEEE 802.3 for
connecting full duplex 10 Gigabit Ethernet (10 GbE) ports to each other
and to other electronic devices on a printed circuit board. It can
comprise two 32-bits datapaths (Rx and Tx) and two 4-bits control flows
(Rxc and Txc), operating at 156.25 MHz DDR (312.5 MT/s). XAUI is a
standard defined in IEEE 802.3. XAUI is a full duplex interface that uses
four self-clocked serial differential links in each direction to achieve
10 Gbps data throughput. Each serial link operates at 3.125 Gbps to
accommodate both the data and the overhead associated with TMDS coding.
The self-clocked nature eliminates skew concerns between clock and data,
and extends the functional reach of the XGMII. SFI is an SFP+ Enhanced
10-Gbps pluggable module high-speed serial electrical interface. It uses
a single variable speed and has about 10 G lanes to carry a 10.0 G signal
and the 64 bit(B)/66 B encoding overhead to yield a 10.3125 G signal.

[0021] The HDMI to XGMII converter 206 can convert the HDMI data signals
transmitted by the HDMI transmitter to the XGMII interface format. HDMI
TMDS data channels 204a (Channel 0), 204b (Channel 1) and 204c (Channel
2) and a TMDS clock signal 204d can be input to the HDMI to XGMII
converter 206, which can convert the signals into an Ethernet IEEE 802.3
XGMII interface. For example, the HDMI inputs may be converted to data
signals (TXD) 210a, control signals (TXC) 210b and a clock signal 210c,
as specified in the IEEE 802.3 standard. In some implementations, there
may be an HDMI to XGMII converter 206 for transmit operations and a
separate HDMI to XGMII converter 206 for receive operations. The HDMI to
XGMII converter 206 may be implemented with an XC5VLX20T (or equivalent)
FPGA, available from Xilinx of San Jose, Calif.

[0022] The XGMII to XAUI converter 212 can convert the XGMII data signals
transmitted by the HDMI to XGMII converter 206 to the XAUI interface
format. The XAUI interface format is standard for extending XGMII between
the MAC and PHY layers. The XGMII data signal 210a, control signal 210b
and clock signal 210c can be received by XGMII to XAUI converter 212 and
converted to a XAUI data signal such as XAUI TX signal 214. In some
implementations, there may be an XGMII to XAUI converter 212 for transmit
operations and a separate XGMII to XAUI converter 212 for receive
operations. The XGMII to XAUI converter 212 may be a BCM8011 (or
equivalent), available from Broadcom of Irvine, Calif.

[0023] The XAUI to SFI converter 216 can convert the XAUI data signals
transmitted by the XGMII to XAUI converter 212 to the SFI interface
format, which is an interface for SFP+ modules. The XAUI data signal XAUI
(e.g., signal TX 214) can be received by the XAUI to SFI converter 216
and converted to SFP+ TX data signal 218. In some implementations, there
may be an XAUI to SFI converter 216 for transmit operations and a
separate XAUI to SFI converter 216 for receive operations. The XAUI to
SFI converter 216 may be a BCM8706 (or equivalent), available from
Broadcom of Irvine, Calif.

[0024] The SFP+ TX data signal 218 can be received by SFP+ optical
transmitter 220 which can convert the electrical signal to an optical
signal which can be transmitted over fiber-optic cable 222 to SFP+
optical receiver 224. The optical signal can be received by the SFP+
optical receiver 224 which can convert the optical signal transferred
over the fiber 222 to a SFP+ Rx data signal 226.

[0025] In FIG. 2, a receive side HDMI-SFP+ adapter/extender 106 can
include one or more of the following: a SFI to XAUI converter 230, a XAUI
to XGMII converter 234 and an XGMII to HDMI converter 238. The receive
side substantially performs the reverse operations of the transmit side,
and thus would be understood from the above. The SFP+ Rx data signal 226
created by the SFP+ optical receiver 224 can be received by the SFI to
XAUI converter 230. The SFI to XAUI converter 230 can convert the SFP+ Rx
data signal to a XAUI Rx signal 232. The XAUI Rx signal 232 can be
received by the XAUI to XGMII converter 234 and can be translated to an
XGMII RXD data signal 236a, a XGMII RXC control signal 236b and a XGMII
Rx clock signal 236c. The XGMII RXD data signal 236a, an XGMII RXC
control signal 236b and a XGMII Rx clock signal 236c can be received by
the XGMII to HDMI converter 238 and can be converted into TMDS data
signals received by the HDMI receiver 242 on TMDS channel 0 240a, TMDS
data signals received on TMDS channel 1 240b and TMDS data signals
received on TMDS channel 2 240c. The XGMII clock signal can be converted
to TMDS clock signal 240d. The HDMI receiver 242 can receive the TMDS
signals which can be displayed by the HDMI Sink 110.

[0026] It will be appreciated that alternatively, a transmit side SFP+
adapter can be created that combines the functions of HDMI to XGMII
converter 206 and XGMII to XAUI converter 212 into a single module using
FPGA (Field Programmable Gate Array) technology. Similarly a receive side
SFP+ adapter can be created that combines the functions of XGMII to HDMI
converter 238 and XAUI to XGMII converter 234 into a single module using
FPGA (Field Programmable Gate Array) technology. Moreover, it will be
appreciated that an integrated circuit chip can be manufactured that
combines the functions of HDMI to XGMII converter 206, XGMII to XAUI
converter 212 and XAUI to SFI converter 216. Similarly, an integrated
circuit chip can be manufactured that combines the functions of SFI to
XAUI converter 230, XAUI to XGMII converter 234 and XGMII to HDMI
converter 238. Moreover, the functions of a transmit side SFP+
adapter/extender 102 and a receive side SFP+ adapter/extender 106 can be
combined into a single transmit and receive SFP+ adapter.

[0027] A standard 802.3 Ethernet frame comprises a preamble (7 octets of
10101010), a start of frame delimiter (I octet of 10101011), a media
access control (MAC) destination (6 octets), a MAC source (6 octets), an
optional 802.1Q header (4 octets), an Ethertype/Length (2 octets), the
payload including data and padding (46 to 1500 octets), cycle redundancy
check information CRC32 (4 octets) and an interframe gap (12 octets).
After a frame has been sent, transmitters are required to transmit 12
octets of idle characters before transmitting the next frame. In
accordance with aspects of the subject matter disclosed herein, the
standard Ethernet frame is adjusted or modified slightly to allow more
data to be sent in each frame, thereby achieving a higher data
transmission rate, as described more fully below.

[0028] The HDMI link operates in one of three modes, a video data period,
a data island period and a control period. During the video data period,
active pixels of an active video line are transmitted. During the data
island period audio and auxiliary data are transmitted using a series of
packets. The control period is used when no video, audio or auxiliary
data needs to be transmitted. A control period is required between any
two periods that are not control periods.

[0029] HDMI can map an 8-bit based RBG video signal to a 10 bit signal.
The extra two bits in the HDMI signal provide for redundancy and error
checking. In accordance with aspects of the subject matter disclosed
herein, when converting the HDMI signal to the Ethernet standard XGMII
signal, the extra two bits can be retained, without removing any
redundancy, enabling an 8 G transmission rate. Alternatively the 10-bit
HDMI framing schema can be converted to an 8-bit format to support a
higher transmission rate. Converting the 10-bit HDMI signal to an 8-bit
signal allows more video data to be transmitted, enabling higher data
transmission speeds. For example, the payload associated with the XGMII
transmit side framing can be an untouched TMDS bit stream if the TMDS
clock speed is less than or equal to 320 MHz. Alternatively, the
apparatus described herein can map 10-bit TMDS data to 8-bit XGMII data
if the TMDS clock speed is greater than 320 MHz. The transmit side
framing can be based on standard 802.3 Ethernet framing, adjusted to
remove identification of source and destination (MAC destination, 6
octets and MAC source, 6 octets).

[0030] Additionally, the idle portion can be inserted or can be removed to
adjust timing differences between HDMI and XGMII data. Thus, In
accordance with aspects of the subject matter described herein, an
example of a format for XGMII transmit side framing can be: 7 octets of
preamble (e.g., 10101010), I octet of start of frame delimiter
(10101011), reserved space comprising 12 octets (no destination or
source), a data field length of 2 octets (12*N+1), 1 octet for an option
byte, 1 octet for DDC (display data channel), I octet for CEC (Consumer
Electronics Control) connection, N bytes of HDMI payload, where
46<=N+3<=1500), 4 octets reserved space, and a 12*M idle pattern
where M<=1. When the TMDS clock speed is <340 MHz and >320 MHz,
bits 4 and 3 of the option byte can be set to 00. In accordance with
aspects of the subject matter disclosed herein, for XGMII transmit side
framing, N (payload bytes) can be set to 3*N1 for a non-video frame. When
N1 lies between 15 and 500, the number selected for N1 can be the largest
number that does not have a remaining fragment that is less than 15
bytes.

[0031] The option byte can be used to identify the type of data in the
signal. For example, bits 2-0 can be set to 111 to indicate that the data
in the frame is generic or unspecified data. Bits 2-0 can be set to 001
to indicate that the data in the frame is video data only or bits 2-0 can
be set to 110 to indicate that the data in the frame is non-video data
only (e.g., audio data or control data). The option byte can be set to
000 to conserve power. Bits 4-3 can be set to 11 to signify that the data
in the frame is untouched, that is that the data in the frame is an
unconverted 10-bit TMDS signal transmission. Bits 4-3 can be set to 00 to
signify that the signal is an 8-bit character decoded from the 10-bit
TMDS encoded video data, re-mapped 10-bit data island and control data to
8-bit. Bits 4-3 can be set to 01=D[7:0] same as option 00, D[8]=bit 9 in
option 1. Bits 7 to 5 can be reserved. In accordance with some aspects of
the subject matter disclosed herein, when the TMDS clock speed is
<=320 MHz, bits 4-3 can be set to 11 and N can be set to 1440 for low
speed transmission using an unconverted 10-bit TMDS data stream. When the
TMDS clock speed is <340 MHz and >320 MHz, bits 4 and 3 can be set
to 00. Video data can be separated into different frames. Similarly data
island and control data can be separated into different frames.

[0032] As described above, the payload associated with the XGMII transmit
side framing can be either an untouched TMDS bit stream if the TMDS clock
speed is less than or equal to 320 MHz or can map 10-bit TMDS data to
8-bit if the TMDS clock speed is greater than or equal to 320 MHz. For
video data periods, TMDS encoded 10-bit data can be decoded back to 8
bit. For data island periods, TERC4 10-bit data can be mapped back to
4-bit data at <D3:D0> and "0000" can be appended at <D7:D4>.
For control periods, 10-bit data can be mapped back to 2-bit control data
at <D0:D1> and "111111" can be appended at <D2:D7>. TMDS
input data rate up to 11.5 Gbps can be achieved.

[0033] On the receive side (conversion of optical signals to electrical
signals), TMDS clock recovery is required because optical signals are not
associated with separate clocking data. To recover TMDS clock
information, a phase-locked loop can be employed. A phase-locked loop or
phase lock loop (PLL) is a control system that tries to generate an
output signal whose phase is related to the phase of the input
"reference" signal. It is an electronic circuit comprising a variable
frequency oscillator and a phase detector. The VSync signal embedded in
the framing and the number of characters in the VSync pulse can be
extracted from the framing and can be used to generate a phase delta for
the HDMI signal. The phase delta is provided to a loop filter which
generates a clean XGMII clock signal which can be used for the clock data
in the HDMI output using the formula fout=fin*10/N.sub.VSync.

[0034]FIG. 3 is a flow diagram 300 of an example of a method to extend
the reach of an electrical cable using a module that converts electrical
signals to optical signals and/or that converts optical signals to
electrical signals. The electrical cable can be an HDMI cable. The module
can be an HDMI-SFP+ adapter/extender as described above, in accordance
with aspects of the subject matter described herein. At 302 a HDMI to
XGMII converter of a first (transmit-side) HDMI-SFP+ adapter/extender can
receive signals transmitted from an HDMI source. At 304 the signals
received from the HDMI source can be converted to XGMII signals using the
transmit-side XGMII framing described above.

[0035] At 306, an XGMII to XAUI converter of an HDMI-SFP+ adapter/extender
can receive signals transmitted from the HDMI to XGMII converter and can
convert the XGMII signals to XAUI signals. At 308 an XAUI to SFI
converter of the HDMI-SFP+ adapter/extender can receive signals converted
by the XGMII to XAUI converter and can convert the XAUI signals to SFI
signals. The SFI signals can be transmitted from the XAUI to SFI
converter to an SFP+ optical transmitter AT 310. The SFP+ optical
transmitter can transmit the optical signals to an SFP+ optical receiver
over a fiber. The SFP+ optical receiver can convert to the optical
signals received from the SFP+ optical transmitter to SFI signals.

[0036] At 312 the SFI signals can be received by a second (receive-side)
HDMI-SFP+ adapter/extender. At 314 the SFI to XAUI converter can receive
the SFI signals and can convert them to XAUI signals. The SFI to XAUI
converter can send the XAUI signals to the XAUI to XGMII converter. At
316 the XAUI to XGMII converter can receive the XAUI signals and can
convert the XAUI signals to XGMII signals. At 320, TMDS clock recovery
operations can be performed as described above to recover HDMI clock
data. At 322 the HDMI signals can be transmitted to the HDMI receiver.

[0037] Implementations of the subject matter and the functional operations
described in this specification can be implemented in digital electronic
circuitry, or in computer software, firmware, or hardware, including the
structures disclosed in this specification and their structural
equivalents, or in combinations of one or more of them. Implementations
of the subject matter described in this specification can be implemented
as one or more computer program products, i.e., one or more modules of
computer program instructions encoded on a tangible program carrier for
execution by, or to control the operation of, data processing apparatus.
The tangible program carrier can be a propagated signal or a
computer-readable medium. The propagated signal is an artificially
generated signal, e.g., a machine-generated electrical, optical, or
electromagnetic signal, that is generated to encode information for
transmission to suitable receiver apparatus for execution by a computer.
The computer-readable medium can be a machine-readable storage device, a
machine-readable storage substrate, a memory device, a composition of
matter effecting a machine-readable propagated signal, or a combination
of one or more of them.

[0038] The processes and logic flows described in this specification can
be performed by one or more programmable processors executing one or more
computer programs to perform functions by operating on input data and
generating output. The processes and logic flows can also be performed
by, and apparatus can also be implemented as, special purpose logic
circuitry, e.g., an FPGA (field programmable gate array) or an ASIC
(application-specific integrated circuit).

[0039] While this specification contains many specific implementation
details, these should not be construed as limitations on the scope of any
invention or of what may be claimed, but rather as descriptions of
features that may be specific to particular implementations of particular
inventions. Certain features that are described in this specification in
the context of separate implementations can also be implemented in
combination in a single implementation. Conversely, various features that
are described in the context of a single implementation can also be
implemented in multiple implementations separately or in any suitable
subcombination. Moreover, although features may be described above as
acting in certain combinations and even initially claimed as such, one or
more features from a claimed combination can in some cases be excised
from the combination, and the claimed combination may be directed to a
subcombination or variation of a subcombination.

[0040] Similarly, while operations are depicted in the drawings in a
particular order, this should not be understood as requiring that such
operations be performed in the particular order shown or in sequential
order, or that all illustrated operations be performed, to achieve
desirable results. Moreover, the separation of various system components
in the implementations described above should not be understood as
requiring such separation in all implementations. Particular
implementations of the subject matter described in this specification
have been described. Other implementations are within the scope of the
following claims. For example, the actions recited in the claims can be
performed in a different order and still achieve desirable results. As
one example, the processes depicted in the accompanying figures do not
necessarily require the particular order shown, or sequential order, to
achieve desirable results. In certain implementations, multitasking and
parallel processing may be advantageous.